Results of both monkey and human trials have highlighted the difficulties in achieving vaccine protection against SIV and HIV. Persistent, recombinant herpesviruses are being used in monkeys to try to match the degree of protection that can be achieved with live attenuated strains of SIV. Results to date have been promising but the absence of anti-Env antibody responses from the recombinant herpesviruses has been a glaring deficiency. The proposed experiments will overcome this deficiency and allow full testing of the promise of this approach.